This invention pertains to the art of painting and more particularly to spray painting a predetermined or preselected area of a workpiece.
The invention is particularly applicable to a method of masking a workpiece in preparation for such spray painting along some demarcation zone and will be described with particular reference thereto. However, it will be appreciated by those skilled in the art that the invention has broader applications and may be adapted to use in other painting environments and applications.
In many industries, it is desired to spray paint finished products and the like so that they will be of one color or tone on one side of some predetermined demarcation zone and of another color or tone on the other side of the demarcation zone. This type of finish painting is often associated with the automobile and appliance industries, although it is utilized elsewhere for other products and product lines. In addition, demarcation zones are present in so-called refinish painting work and in painting work performed subsequent to some product or workpiece surface repair. In order to obtain satisfactory or aesthetically pleasing results, it is necessary to mask the product at least along the demarcation zone to prevent paint overspray onto adjacent areas of the product which are not to be painted.
Various paint masking systems have been known in the art for many years and include, for example, use of conventional masking type tape or the like. In the most basic of these prior systems, the masking tape is affixed to the workpiece with one tape side edge disposed coextensive with the demarcation zone. This then separates that portion of the workpiece surface which is to be painted from that portion which is not to be painted. Moreover, the tape is also typically used to retain paint drapes of paper, cloth or the like in position over at least that section of the workpiece portion to be protected adjacent to the demarcation zone.
One particular drawback to this type of general masking system is that when the tape and other mask materials are removed from the workpiece following painting, a distinct paint ridge is defined along the demarcation zone. Thus, it is necessary to utilize further finishing steps to remove or blend the ridge into the remainder of the workpiece finish. Other problems with these prior masking systems reside in the extremely cumbersome installation procedures required and the close correlation between the overall success of the mask and the ability and/or experience of the mask installer. Still further, the final painting costs are increased because of the necessity for performing separate finishing steps for removing or blending the paint ridge at the demarcation zone.
Through the years, many attempts have been made at improving the aforementioned general type of paint mask system for reducing or entirely eliminating the problems generally associated therewith. All of these various improved systems have, however, still had associated problems during application and use. Consequently, entirely satisfactory mask installation and painting results could not be reliably achieved. Moreover, such systems oftentimes still necessitated some type of finishing work at the demarcation zone following painting and mask removal.
By way of specific example, one improved mask arrangement is shown and described in U.S. Pat. No. 3,930,069 to Stephens. The system there disclosed utilizes a non-metallic protective tape which includes an adhesive backing over a portion of one face thereof and applied in a manner such that the tape face has a straight longitudinal junction line therealong defining the adhesive backed portion from a non-adhesive backed portion. The tape is applied to a workpiece so that the longitudinal junction line between the adhesive and non-adhesive areas corresponds to a predetermined demarcation zone with the non-adhesive area extending over a portion of the workpiece area which is to be painted. Thereafter, the non-adhesive backed portion of the tape is manually bent away from the workpiece so as to define a tapered, outwardly opening pocket diverging from the workpiece. Paint is then sprayed onto that portion of the workpiece which is to be painted and into the pocket area defined by the mask. Paint applied within the pocket is feathered toward and terminates at the demarcation zone. A last or final coating of solvent is sprayed or otherwise applied to the paint to feather it along the demarcation zone to a minimum thickness in an effort to achieve blending with the adjacent painted area. Following mask removal, any paint ridge or edge line remaining along the demarcation zone is removed or rubbed out through use of a suitable rubbing compound.
While the method and arrangement disclosed in U.S. Pat. No. 3,930,069 has found some commercial success, it too has several drawbacks. For example, the protective tape is only viably useful for demarcation zones or break line areas which have generally straight line configurations. Demarcation zones or break line areas which are curvilinear or are otherwise unusually configured are very difficult to mask using this system. Indeed, in such situations, the ability and experience of the person applying the mask again plays a very significant role in determining the overall aesthetic success of the final paint finish obtained.
Further, in manually bending the non-adhesive backed portion of the tape from association with the workpiece, the inherent resiliency or memory of the tape will oftentimes cause that tape portion to drift back toward engagement with the workpiece. Thus, the mask requires close monitoring during the painting process with continual manual rebending of the non-adhesive backed tape portion. Variations in the amount of such bending can also affect the overall surface finish obtained adjacent the demarcation zone and cause undesired variations therein. In addition, some final finishing steps following mask removal are required to obtain satisfactory blending and/or removal of a paint ridge created along the demarcation zone. The reason such further steps are needed is due simply to the basic construction of the tape and its cooperative relationship with the workpiece. That is, the interface or junction between the adhesive backed and non-adhesive backed portions of the tape provide a natural ledge area along the demarcation zone to thus allow paint accumulation and create the undesired paint ridge.
It has, therefore, been considered desirable to provide a further improved method for masking which would overcome the foregoing practical problems encountered in using previously known masking methods and techniques. The subject invention is deemed to meet these needs as well as others. The invention provides a new and improved method of masking a workpiece which is simple, effective, accommodates masking along demarcation zones which have many different configurations, provides an acceptable finish at the demarcation zone requiring no further finishing steps and is readily adapted for use in a wide variety of applications.